Phased array radar systems often include numerous transmit and receive integrated microware modules housed in an equipment rack. See U.S. Pat. No. 6,615,997 incorporated herein by this reference. See also U.S. Pat. Nos. 6,903,931; 5,901,037; 5,998,240; 7,115,987; 6,903,929 and application Ser. No. 11/447,488 also incorporated herein by this reference.
Among other circuitry, each main module includes two to eight transmit and receive modules each located on a cold plate. Each transmit and receive module includes microwave circuitry built upon a gallium arsenide epitaxial layer to form a monolithic microwave integrated circuit (MMIC) in electrical communication with the transmit and receive structure of the main module. This integrated circuitry is conduction cooled via the cold plate which itself is cooled via an interface through the main module conductively coupled to structure within the equipment rack. A coolant circulates through the equipment rack for this purpose.
It is often desirable to provide more power to the microwave integrated circuitry. One proposed design includes the use of a gallium nitride epitaxial layer base for the microwave circuitry instead of gallium arsenide to operate at higher power levels. 10-20 W/mm gate power levels are expected in gallium nitride monolithic microwave integrated circuits in the future.
But, with greater power levels comes more heat and the traditional heat transfer configuration may not be able to sufficiently dissipate the heat generated by the gallium nitride monolithic microwave integrated circuits. At the same time, any new heat transfer configuration optimally does not adversely effect the present configuration of the main transmit and receive module or its form, fit, and function with present equipment racks and other sub-systems of the radar system. Extensive architectural changes to the radar system and subsystems are not desirable.
Due to the tight space between modules in the equipment rack, cooling methods available to cool the integrated circuitry are somewhat limited. Also, each module must be easily replaceable in the field.
Existing microcoolers are not suitable for cooling gallium nitride monolithic microwave integrated circuitry. Such microcoolers do not contain the required heat transfer area or incorporate advanced materials such as diamond. In addition, existing microcoolers are not based on advanced fabrication methods such as multilayer wafer bonding and deep reactive ion etching of silicon carbide and diamond or feature the use of multi-phase heat transfer as may be required for embedded gallium nitride MMIC cooling.